The disclosure relates to an electropneumatic field device, such as an electropneumatic position controller, an I/P transducer, or the like. The electropneumatic field device is often used as a control device for controlling a pneumatic actuator of a processing plant, for example in the petrochemical industry, the food industry or the like, which in turn actuates a control valve for regulating a process fluid flow.
The electropneumatic field device has at least one electrical field input, via which the field device receives an electrical field input signal, which for example in the case of a pneumatically operated control valve can be formed as a set-point control signal. The field input signal can for example be an analog 4-20 mA current signal or else a digital field bus signal, such as Profibus PA, Foundation Fieldbus, ASI or Devicenet. Furthermore, the electropneumatic field device has at least one electronic and/or pneumatic component, which is for example an electropneumatic transducer, a data memory, a pneumatic current generator and/or a microprocessor. It shall be clear that the electropneumatic field device can have a plurality of electronic and/or pneumatic components, such as a plurality of electropneumatic transducers, microprocessors, electrical switches, data memories and/or pneumatic current generators. The at least one electronic and/or pneumatic component is connected to the at least one electrical field input, in order to obtain the electrical field input signal. It is known, particularly if a position controller is used as the field device, that an open loop and/or closed loop control electronics can be interconnected between the electrical field input and the electronic and/or pneumatic component. In case of an electropneumatic transducer as the at least one electronic and/or pneumatic component, the electropneumatic transducer is pneumatically coupled to the pneumatic supply input of the field device. The field device usually has a pneumatic field output, at which a pneumatic field output signal for example for controlling the pneumatic actuator can be output on the basis of the field input signal received.
An electropneumatic field device is known from DE 10 2008 053 844 A1, in which a plurality of electronic and/or pneumatic components, such as an electronic regulator, a U/I transducer, an I/P transducer, a power amplifier, and also an inverting amplifier can be used. An inverting amplifier is used when the electropneumatic field device accesses a double-action pneumatic actuator.
A position controller for controlling and/or regulating a pneumatic actuator is known from EP 1 138 994 A2. The position controller has a main housing and a removable maintenance cassette, the interior of which is divided into a partition for electropneumatic assembly elements and an electronics partition. The entire maintenance cassette can be removed from the main housing for maintenance purposes.